Military uniform fabric patches treated with permethrin were evaluated against natural and laboratory strains of human body lice, Pediculus humanus, L. Permethrin-treated fabric was toxic to body lice on contact and quickly affected feeding behavior and the likelihood of disease transmission, even when washed up to 20 times. The use of permethrin-treated clothing offers a new passive approach in human louse control not previously feasible. Military personnel wearing permethrin-treated uniforms, therefore, can expect significant and long-term protection from lice and louse-borne diseases in endemic areas.